Drawer cut out for undermounts in the field

[Chris Hughes]

Someone PM'ed  my a few questions about how to cut out the back of a drawer for undermounts a little while ago.  I answered the questions but never heard for him again so I don't know if he understood the technique and thought it a waste of time or if he didn't understand it at all.  Either way I thought I would put together a pictorial and a brief explanation.  It a very quick and easy way to knock out the slots in drawers whether in the field or shop.

One of the benefits of the Festool system is the ability to do high quality work in the field without the overhead of the shop.  The ability to build strong draws without fasteners revealed using the Domino.  A trend in cabinet design has been the replacement of side mount slides with undermount slides.  The use of this hardware is as straight forward as any.  The two brands I use and see most are Blum and Salice are almost identical in drawer sizes and requirements for the cabinet sizing.

One the questions asked was, "How big is the cutout in the back of the drawer for the hardware to pass through?"  For those new to undermount hardware, the drawer box sits on top of the slides and is fastened only with a release on the front and a barb at the back of the slide that protrudes into the drawer back to keep the drawer from tipping.  The width of the cut out varies a little between brands, but I have found that 1 1/4" from the inside of the drawer sides. 

The next question was, "how do you cut a 1 1/4" slot through the back of a assembled drawer box?".  I have observed many shops using a table saw and dado set with multiple passes to accomplish the feat.  When I first started using undermount slides that is how I set up as well.  I found the process problematic.  If the sides varied in width, if the material depth beyond the drawer bottom varied, setting up to cut the left side versus the right, the availability of the stable saw and dado set when in the field were all issues I found with the common technique.

I found that I could simplify the work of the cut out by using a flush cut hand saw and a router with a large dovetail bit. 

step one.  Flip the drawer box over and rotate the back of the drawer towards you.  Measure from the inside of the side and mark at 1 1/4" a square line and extend down about a half an inch.  This line is the guide for the "control" cut toward the inside of the drawer back.

step two.  Using a flush cut saw, cut along your line until you reach the drawer bottom.  This will prevent tear out.

step three.  Set up a router with a large diameter dovetail bit.  set the router on the drawer sides to set depth of cut.  Plunge bit until it makes contact with drawer bottom.  You should be able to move router freely while making contact with bottom for proper adjustment. 

step four.  Move the router to the outside of the drawer box to cut a horizontal control cut, similar to the technique we would use when cutting a dovetail joint.  This will prevent tear out on the back of the drawer.  After the control cut in complete, move the router aback to the inside of the drawer bottom.  Start the cut away from the drawer side and the control cut.  This allows you to walk the bit to the control cuts, kind of staying inside the lines.  Move the router back and forth between the margins.  Once the bulk of the material is removed make a pass along each control cut for cleanup.

Bob's your Uncle, you have made your knock out without a table saw and it was both clean and quick.

The only thing you have to do next is attach the quick releases on the front bottom side of the drawer and drill a couple of hole in the back for the barbs on the slide.

The releases are self explanatory and vary between brands so I won't go into that.  The holes in the back vary as well between brands in their placement but most use a 6mm or 1/4" bit.  There are jigs available for placement but I have found it very easy to place the holes by sliding the drawer into place and giving a light tap to indent the drawer back.  Using a 1/4" bit, drill a hole about 3/8" deep. 

 

[ThomasC]

Good ideas, Chris.
I usually notch the drawer backs before assembly with either a jig saw or band saw. Your method works better if the drawer is already assembled.
One question/comment: Most of the undermounts I use (Grass/Mepla & Blum) are designed for drawer sides that are a maximum of 5/8" thick. I know Blum offers a model that accomodates 3/4" material. Is that what you're using on the drawers in the photos? I just wanted to remind people to check the specs of the drawer slides before building a bunch of drawers that may not work with certain slides.

TC

 

[Chris Hughes]

Yes the drawers I used were 3/4 inch.  I like Salice slides but I don't think they will work with 3/4" material.  My perferred method and material is 5'8" baltic and dovetail.  I working with a contractor that uses a standard box being 3/4" nailed together.  I converted them to a domino box to get rid of the exposed joinery. 

 

[Billnut]

The sides of the draw box can be any thickness.  Only the 1/2" of the drawside below the box needs to be 5/8".  I have used 3/4" for the sides and just thinned out the  bottom portion when I only had certian size slides.

Bill
Bonetto's Carpentry

 

[Chris Hughes]

Good idea.  I thought that the material thickness had more do with the tolerance of the sides.  It hit me this weekend on a project that required me to go off the manual that fronts and backs had influence on hardware placement.  The drawer in my pictorial has an integrated front in order to match drawers that sit in the adjoining cabinet.  The drawers had a glass bottom and so sidemounts were spected.

 

[fshanno]

I use a pull saw and a chisel after assembly.  Make the cuts then a couple of blows with the chisel on at the bottom to act as deep scoring and just break off the piece.  It always breaks clean because of the groove for the bottom.

 

[Chris Hughes]

I usually build plywood boxes.  It requires way to much shop time making stock.  If the job requires solid wood boxes then I would probably order them.  I'm starting to like the domino drawer.  It's not as elegant as a dovetail box but it is a nice drawer with no exposed fasteners. 

Anyhow, chisels don't work as well on plywood as a carbide cutter and certainly not as fast.

 

[Wonderwino]

Looks easy, Chris!  Do you lay a small handscew or some other type of stop on the edge of the back to control the router?  Could you make a jig that would clamp over the drawer bottom for repeatable precision and a bigger base to support the router?

 

[Chris Hughes]

I found that I have adequate support for the router base as it sits on two axis provided by the drawer side and back during the entire routing process.  I thought about a jig, but the first rule of process enieneering is, " keep it simple".  If the router was not supported and was tippy I would not attempt the cut.  It is important to be able to get consistent results.

 

[fshanno]

I usually build plywood boxes.  It requires way to much shop time making stock.  If the job requires solid wood boxes then I would probably order them.  I'm starting to like the domino drawer.  It's not as elegant as a dovetail box but it is a nice drawer with no exposed fasteners. 

Anyhow, chisels don't work as well on plywood as a carbide cutter and certainly not as fast.

I tried it and you're right, it's faster and nicer with the router.  Plus, my notches in plywood were pretty ragged. 

I tried it with a spiral bit in my Colt and it worked great.  I can even be done without the starting cuts.  Just make a shallow climb cut on both sides as you said and it minimizes tearout. It worked great! 

I even tried it pre-assembly with four backs ganged together.  Again it worked great.

I still use the chisel though.  A 1 1/4" chisel is perfect for marking the lines. 

 

[honeydoman]

I just use my Fein multi master quick and easy ?